Magnesium base alloy



htented Apr. 14, 1942 MAGNESIUM BASE ALLOY John C. McDonald, Midland,Micln, assignor to The Dow Chemical Company, Midland, Micla, acorporation of Michigan No Drawing. Application December 23, 1940,Serial No. 371,382

3 Claims.

The invention relates to magnesium base alloys and more particularlyconcerns an alloy of this nature having high tensile and yield strengthsassociated with a degree of formability desirable for formingoperations.

Magnesium base alloys are being widely used in the structural arts wherea light weight metal is highly desirable, -such as for use in makingcastings, forgings, and the like. However, the use of these alloys inthe rolled form to make sheet metal articles requiring formingoperations, such as bending and drawing, has not progressed as rapidlydue to the fact that, in general, alloys havinggood iormability orductility permitting relatively sharp bends to be made without the.

'article developing external cracks, usually have inferiorcharacteristics as regards their tensile 4 and yield strengths.

magnesium containing the ordinary impurities found in the commerciallypure metal, such as traces of nickel, copper, silicon, and iron. Aparticularly desirable composition having a preferred combination ofproperties is one containing 3 per cent of silver, 3 per cent ofaluminum, 5 per cent of cadmium, 3 per cent of zinc, and 0.3 per cent oimanganese.

The following table lists some of the properties of rolled sheet metalmade from my new polynary alloy and compares these properties with thoseof related alloys. The new alloy is shown to have improved yieldstrength and tensile strength. The table also shows that the per centelongation which is to be regarded as a measure of the Iormability orductility of the alloy is of the high order necessary to render thealloy suitable for forming operations.

Table Nominal composition in percent (remaindekmagnesium) Annealed Coldrolled Percent Yield Tensile Yield Tensile Ag Al Cd Mn Zn elongationstrength in strength in strength in strength in in 2 inches lbs./sq. in.lba/sq. in. Ilia/sq. in. lbs/sq. in.

3 10 r 0.5 3 18 28,000 43,000 44,000 52,000 0 10 0. 5 3 i2 20, 000 40,000 45, 000 51, 000 6 3 0. 5 3 i0 32, 000 47, 000 47, 000 52, 000 6 3 100.5 18 ,000 45,000 ,000 50,000 6 3 10 0. 5 3 13 31,000 ,000 40,00055,000

It is, accordingly, the principal object of the invention to provide amagnesium base alloy which can be made into rolled sheet and the likepossessing a sumcient degree of ductility or formability at ordinarytemperatures to be sharply bent, drawn or otherwise shaped, while havinggood tensile and yield strengths.

Other objects and advantages will be apparent as the description of theinvention proceeds.

My invention resides in the discovery that a magnesium base alloycontaining from about 0.4 to 12 per cent of silver, 0.3 to 10 per centof aluminum, 1 to 15 per cent of cadmium, 0.3 to 6 per cent of zinc, andfrom 0.01 to l per cent of manganese possesses the aforementionedproperties. The term magnesium" used herein and in the appended claimsis intended to include The properties set forth in the above table underthe term "annealed" were obtained by first rolling the alloys at atemperature of 600 to 650 F. and thereafter annealing them at varioustemperatures through a temperature range of from 400 to 800 F. Theproperties selected for the table were those of the annealed specimenswhich exhibited the maximum elongation. The properties set forth underthe term cold rolled were obtained by subjecting specimens of the Acomparison of the properties listed in the above table shows that whenthe new alloy contains relatively small amounts of cadmium, the alloypossesses an exceptionally high degree of formability coupled with hightensile and yield properties. It will be noted that the combinedproperties of the new alloy are superior in every instance to those ofrelated alloys. In the higher percentage range of cadmium it will benoted that the iormability characteristics, while still satisfactory;tend to fall of! some while the tensile and yield properties.markedlyimprove. Thus, the particular composition selected will dependupon the use for which the'specific composition is intended. Forexample, in those instances where a high degree of formability is ofprime importance a composition will be selected containing lowerpercentages of cadmium, while in those instances where high tensile andyield properties are of prime importance higher percentages of thealloying ingredient cadmium will be employed.

While the new alloy is very useful in wrought form due to itsformability characteristics, it may also be suitably used for makingcastings, extruded forms and the like. It is further pointed out thatthe new alloy is amenable to solution and precipitation heat treatments'which accordingly modify its properties.

The new alloy may be compounded by any of the methods usually employedformelting' and alloying metals with magnesium, "suchas by adding thealloying ingredients singly or jointly to a bath of molten magnesiumwhich'is preferably protected from oxidation by a suitable It should bementioned that. the amount of manganese that may be present in a givencomposition is dependent upon the amount of aluminum present. Forexample, when about 0.5 per cent aluminum is present, it is diificult toobtain an alloy, containing more than 1.0 per cent of manganese Incompositions containing more aluminum, such as from 8 to 10 per cent, itis diil'icult to obtain an alloy containing more than 0.5 per cent ofmanganese.

It is to be understood that the invention is not limited to the specificcomposition herein described, but may take other forms without dcpartingfrom the scope of the invention.

I claim:

1. Amagnesium ,base alloy containing from 0.4 to 12 per cent of silver,from 0.3 to 10 per cent of aluminum, from 1 to 15 per cent of cadmium,from 0.3 to 6 per cent of zinc, and from 0.01 to 1 per cent ofmanganese, the balance being magnesium. v

2. A magnesium base alloy containing 3 per cent of silver, 3 per cent ofaluminum, 5 per cent of cadmium, 3 per cent ofzinc, and'0.3 per cent ofmanganese, the balance being magnesium.

3. A magnesium base" alloy containing from 0.4 to 12 per cent of silver,0.3 to 10 per cent of aluminum, 1 to, 15 percent of cadmium, 0.3 to 6per cent of zinc, and 0.01 to 1 per cent of manganese and characterizedby improved tensile and yield strengths inthe cold rolled state ascomparedto a similar alloy devoid of aluminum.

' JOHN c. MCDONALD.

